JPH11346380A - Communication system and method for hand-off and drop-off of cellular radio telephone set supported by positioning system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To smoothly execute hand-off by establishing an exact position from an obtained satellite signal in a positioning system, and transferring the position information to a cell base station for operating the drop-off or hand-off of a cellular radio telephone set to another base station or frequencies based on the quality level of a communication signal. SOLUTION: A radio telephone set 20 is provided with a positioning system 22 such as a satellite position measuring system (GPS) for deciding the position on earth. This information is transferred to a base station 24 so as to be used for a drop-off or hand-off operation. Also, the radio telephone set 20 is provided with a positioning system memory 26 for storing a database having the astronomical ephemeris of each satellite 40. This memory 26 is composed of a non- volatile RAM, and when the operation of the satellite 40 is stopped or the orbit of the satellite 40 is changed, a service radio telephone set 20 is allowed to update the astronomical ephemeris data.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for handoff and dropoff in a cellular communication system, and more particularly to a technique for establishing whether to perform a handoff or a dropoff for a cellular radiotelephone that emits a weak signal. About.

[0002]

2. Description of the Related Art A radiotelephone system consists of a number of base stations, also called cell sites. Each base station is coupled to one mobile switching center (MTSO), which is connected to the public switched telephone network (PSTN). Each of the base stations includes an antenna for receiving and radiating radiotelephone signals for communicating with the cellular radiotelephone and for switching radiotelephone signals from the cellular radiotelephone to the mobile switching center. The base station also enables communication with the wireless telephone by providing an appropriate channel to the wireless telephone. The mobile switching center switches signals from the base station to the public switched telephone network and switches signals from the public switched telephone network to the base station.

Generally, a code division multiple access system (CDM)
A) and spread spectrum systems have not been used previously because they are useless in mobile wireless environments due to near-far problems. Perspective problems arise in cellular communication systems, where different transmitters interfere with base station transmitters. In a mobile radiotelephone environment, a user may be near or far from a base station. The difference in the loss of the propagation path between these users having extremely different distances may reach several tens of dB.
This causes the link capacity to decrease on average over the whole. In spread spectrum systems such as CDMA systems, anti-jamming capacity helps in such situations, but unfortunately is not enough to overcome the difference between strong nearby interfering signals and attenuated distant signals. Not enough. In CDMA systems, codes are used to identify signals. If enough codes can be used for identification, the limit on the number of users is determined by the system jamming margin. This is because the receiver will operate as long as the total power of all the unwanted signals does not exceed the power of the desired signal by more than the jamming margin.

[0004] It has been estimated that all mobile radiotelephones in a cell transmit constant power. However, the benefits of a spread spectrum system are realized if the transmitter can be controlled so that the power level received from all users, rather than a constant power, can be changed to be approximately equal. The Rukoto. In systems where the received power is controlled, multiple subscribers can occupy the same spectrum, resulting in the expected interference averaging benefits. However, systems that employ power control to solve the near-far problem within the cell suffer a significant loss in receiver sensitivity. This is because, to maximize the number of simultaneous users, all signals must reach the receiver (base station) at equal power levels. If each radio telephone detects the distance from the base station and adjusts the output power accordingly, so that the base station can receive a signal at a predetermined signal power level, the power control in each radio telephone is realized. Will be done. Otherwise, the mobile transmitter emitting the weakest signal directs the action of other cell users, especially near the edge of the cell. The cell user receiving this instruction changes the transmission power of the cell user according to the instruction, thereby providing power to the user who emits this weak signal.

[0005] A handoff by one cell base station to another cell base station is performed by improving the transmission by requesting all units in the new cell to raise their transmit power to that level. This is to cause jamming of the station, thereby preventing an increase in the transmission signal power of the radio telephone located at the cell edge. However, if the user's signal was very weak, the radiotelephone would have to be dropped off of the cell by the base station before wiping out the entire network. Users that emit very weak signals are not handed off to other cell base stations. This is because, after being handed off, the performance of the user at the edge of an adjacent cell is poor.

In a power controlled CDMA system, if adjacent cells have one base station that can be received by several base stations, the radiotelephone in that cell will have a soft handoff. It is necessary to communicate with all of those base stations in order to realize. Soft handoff, also known as "connection before disconnection"
As implemented in the system, all cells use the same frequency (as defined in the IS-95A standard). In soft handoff, it is possible to connect to neighboring cells before leaving the current cell. With soft handoff, less power is required, which reduces interference and increases capacity. In soft handoff, control is passed to the base station that is most convenient to serve the user. During a soft handoff,
The user remains in full communication with all other base stations. When the radiotelephone reaches the edge of the cell, the controlling base station assists in handing off the radiotelephone to transfer control to another cell. However, since the base station does not know the location of the wireless telephone, all the wireless telephones in the cell must be paged and wait for a response. This process takes a lot of time. The base station determines a handoff or dropoff candidate from the received response.

[0007] In a power controlled CDMA system, each cell participating in the soft handoff is:
Transmit the same traffic stream bit by bit to the mobile radiotelephone. This is done on any available code channel. Each base station must select a code channel based solely on availability. The radiotelephone implements multiple fingers at the RAKE receiver. With multiple fingers, "tuning" is generally possible to any of the 63 available code channels. A backward power control bit is embedded in the forward CDMA channel. Each of the power control bits is interpreted as a command to increase or decrease the power in about 3/4 dB units. Each of the base stations
Determine power control independently. The mobile station demodulates power control bits and raises and lowers power accordingly. The purpose of power control is to maintain the reverse link transmit power at the lowest possible level commensurate with error operation. Therefore, the mobile radiotelephone must interpret the power control bits because it only needs to power up when all base stations involved in the handoff indicate "up." However, this interpretation often does not agree. If any of the participating base stations indicate "down," the mobile radiotelephone must power down. This rule says "down
OR ".

In a CDMA system, MAHO (Mobile Assisted
Handoff) is used. That is, in practice, the mobile radiotelephone continuously searches for pilot codes, which use PN correlators specially designed for this purpose. All base stations use the same code. If the mobile radiotelephone was already informed of the CDMA system time (ie, if it was already in the call, it would have been), report the relative timing of the newly detected pilot. be able to. Base stations are distinguished by the phase of the pilot. The period of each pilot is 26.667 milliseconds.
The pilot is divided into 64 chips as a minimum unit.
64 chips is about 52 milliseconds, which is about 15 kilometers at the speed of light. The timing of the mobile radiotelephone is usually so good that the reported pilot offset clearly identifies the base station it detects.

A mobile radiotelephone reports pilots based on a "pilot to interference ratio" (PIR). The PIR is compared to an absolute threshold to determine when the mobile radiotelephone is reported as a candidate for handoff. The absolute threshold, or first threshold, is a parameter obtained by the mobile radiotelephone from overhead messages broadcast by the base station. When there is a pilot that exceeds the first threshold, its presence is reported to the network via a message. The network adds the base station to a so-called active set. The active set is a set of base stations participating in the soft handoff of the mobile radiotelephone. The second threshold, which is relative rather than absolute, is the largest PIR in the active set and the P of each of the other members.
Compared to the difference from IR. If there is a difference below the second threshold, another message is sent. Normally, this would result in the base station being removed from the active set and a message sent to that effect sent to the mobile radiotelephone.

The two thresholds, one absolute and one relative, ensure that any station that can contribute to the overall signal-to-noise ratio in any useful way will have a high probability of entering the active set. Produces the effect of Conversely, a base station is only removed if it is much degraded from the best station. If the best station is located at the edge, the next strongest station is kept. The effectiveness of these two threshold configurations has been found by experience, but has the disadvantage of sometimes too many handoffs. Too many handoffs reduce capacity.
This is because the number of forward traffic channels required for its support becomes too large. Excessive handoffs also limit the number of channel elements required by the base station, such as CDMA modems.

[0011] Support for forward link power control is different for cellular and PCS air interface standards. In IS-95A and Rate Set 1 of the J-STD-008 standard, only forward power control based on message transmission is specified. That is, if it determines that its own forward signal quality is low due to the excess of the frame error rate, the mobile wireless device sends a report to the base station. This method is relatively slow due to processing delays in interpreting messages at the base station. 14,4
Rate Set 2, a 00 bps set, includes a faster forward power control mechanism. Each of the backward traffic frames includes a bit that reports erasure with even a small processing delay.

In some communication systems, it is difficult to perform a handoff from one base station to another base station without knowing the exact location of the radiotelephone. This is particularly the case for CDMA systems that have to hand off to base stations with different carrier frequencies. CD
In a cellular system based on MA, the base station supervises 1
Although only one carrier frequency is used for all wireless telephones in one area, surrounding base stations may use different carrier frequencies. When the signal of the radiotelephone is weak, CDMA where each of the base stations emits a different carrier frequency if weak at the edge of the cell
In the system, a transmission of a new carrier frequency by a new base station is not received by a radiotelephone having a weak signal that does not know the new carrier frequency. In this case, the handoff is not completed, and the wireless telephone cannot be used. In addition, the ability of other cellular radiotelephones in the cell to transmit can be compromised.

Therefore, there is a need to identify the radiotelephone with a weak signal and perform a handoff or dropoff of the radiotelephone by the base station of the cell. According to conventional methods, a base station can only determine that a weak radio telephone is within a predetermined range without knowing its exact location. Furthermore, since the base station can only recognize a radio telephone responding to paging from the base station,
It takes time to reach a wireless telephone with a weak signal.

FIG. 1 shows an example of a cellular communication system / cell network. In an actual cellular communication environment, the sizes and shapes of the cells 10, 11, and 13 change. The cellular system of FIG. 1 is an analog or digital communication system and employs a code division multiple access scheme (C
One or more of multiple access modulation mechanisms such as DMA, time division multiple access (TDMA), and frequency division multiple access (FDMA) can be adopted.

When disconnecting a wireless telephone, it is determined which wireless telephone 12 is powered on, and
12 must determine which cell base station 14 or 15 it is receiving. To find the wireless telephone 12, the cellular system sends a message, usually called a page,
Broadcast in many cells 10,11,13. Wireless telephone 12
Responds, the cellular system continues to pass the call, and then communicates to one of the cells 10, 11, 13 containing the wireless telephone 12. If the system is a wireless telephone 12
If the location is not known, the page must be broadcast in all sectors of cells 10, 11 and 13. As the traffic of cellular communication systems increases, the communication resources that support system-wide paging in large metropolitan areas become enormous. Because each of the radiotelephones 12 registers with at least one base station 14,15 to inform its cellular system of its location and to receive pages controlled by one or more base stations 14,15. Because you have to do it.

When the power is turned on, the radio telephone 12 usually needs to search for and acquire a pilot signal. The pilot signal of the CDMA system is continuously transmitted from the base station 14. The radiotelephone 12 obtains the initial synchronization of the system and the exact time, frequency,
And use the pilot signal to define phase tracking. Generally, it takes a few seconds to acquire a pilot signal. This is mainly due to the close proximity of the cell base station 14 to the radiotelephone 12 and the fact that the cell 10 is in place. When you find the strongest signal, your wireless phone
12 registers with the cell base station 14 that is emitting the signal.

Referring to FIG. 2, typically, upon registration, the radiotelephone 12 transmits identification parameters via a transceiver. These parameters include the serial number and the associated telephone number or number. The registration information is received by a transceiver located in the base station 14 corresponding to the cell 10 containing the wireless telephone 12. This registration information is transmitted by the receiving base station 14 to the mobile telephone switching office (MTSO).
It is relayed to 16. One function of the MTSO 16 is to route calls between the public switched telephone network (PSTN) 18 and the various cells 10. Generally, MTSO 16 also includes a database having information related to the cell structure.

In a CDMA cellular communication system, the radiotelephone is paged to various cells to identify the cell in which the radiotelephone is located and route the call. This type of communication system needs to determine the cells in which the radiotelephone may be located. By performing a process known as registration, it is possible to identify the group of cells where the wireless telephone is most likely located. In the zone registration technique, the cellular system is divided into zones, so the paging amount of the system is small, and the wireless telephone is paged in all cells in the zone. For this purpose, the wireless telephone normally keeps a list of zones that it has visited recently, and registers as a new zone when entering a zone that is not on the list. Cell base stations 14, 15,
Each of the 17 broadcasts in the zone to which it is assigned. When a wireless telephone is registered in a specific cell, the MTSO determines a zone using the cell structure database according to the distance between the wireless telephone and the cell. When a call to be transferred to the wireless telephone is received at the MTSO, the MTSO instructs the cell corresponding to the zone in which the wireless telephone is registered to send a paging message to the wireless telephone.

Upon completion of the paging by the cell base station in the determined paging zone, the radiotelephone may be in the current zone or the current or past location when it is still in the zone and under conditions to receive the page. The mobile station responds to the received page by transmitting a response message received by the base station of the cell that has performed the communication. The response to this page is relayed by the receiving cell base station to the mobile switching center. The mobile switching center identifies the cell where the wireless telephone is currently located by relaying the response by the cell base station. The mobile switching center routes the calls to be transferred from the radiotelephone to the base station corresponding to the cell in which the radiotelephone is located.

According to the conventional "registration method based on distance", each cell base station transmits its position information and a predetermined limit distance value. In this method, each radiotelephone communicates with the radiotelephone based on the transmitted current cell base station location information and the previous cell basestation location information with which the radiotelephone was previously registered. Calculate the distance between the located cell and the cell base station. Thereafter, the radiotelephone determines whether the distance of the radiotelephone is greater than a predetermined limit distance value from the previous cell by comparing the calculated distance with the limit distance value from the previous cell base station. If the calculated distance is larger than the previous cell base station limit distance value, the current cell base station is registered. The registration information is relayed to the mobile switching center to determine the paging cell zone of the wireless telephone. The wireless telephone stores the zone information in its memory.

[0021] AMPS (Advanced Mobile Phone System)
Systems such as GSM use a timer or counter method to determine the location of a wireless telephone. In a cellular system using the timer method, each wireless telephone registers with a base station every few seconds. The moving speed of the cellular radiotelephone is estimated, and the distance traveled by the radiotelephone is estimated from the last registered time. However, AMPS handoffs often fail and calls are dropped. This contributes to the perception that the service quality is poor. Furthermore, before and after each handoff, the link quality deteriorates over a long period of time, causing unpleasant noise and distortion.

In another conventional method, the base station determines the boundary of the area covered by the base station based on the profile representing the class. This contour shape has minimum and maximum boundaries generated based on the RF measurements of each base station. The intersection of the outline shapes representing the grades determines the polygonal region that borders. This polygonal area represents the position of the cellular radiotelephone used for error evaluation. When the center of the polygon is determined, the position address of the wireless telephone is determined by referring to the database. Further, in a satellite communication system, another CDMA method based on distance control can be used. In this way, handoff by the receiver of the mobile radiotelephone is possible. The receiver in this method drops one satellite and synchronizes with the other satellite by switching using the known position of the receiver and the known position of the transmitter.

At present, when the mobile radiotelephone is operating in the digital CDMA mode and moving toward the AMPS only area, that is, when the base station handles only analog signals, if the mobile radiotelephone is possible, Handover must be performed by switching the mobile radiotelephone from digital mode to analog mode, and the radiotelephone must continue in analog mode, which is not always preferred. Further, the IS-95A standard stipulates that all CDMA base stations and wireless telephones should have both analog and digital modes in the future. In such a system, when the radiotelephone is in a disadvantageous reception area, i.e., when the digital transmission is weak and may weaken other mobile phones in a power-controlled CDMA system, the analog-to-telephone system may be used.
By switching to the mode, it may be necessary to perform a soft handoff. However, IS-95A
The standard does not provide an option to revert to digital mode.

[0024]

SUMMARY OF THE INVENTION It is a first object of the present invention to overcome the above disadvantages associated with the prior art and to perform a handoff smoothly by obtaining accurate information on the location of a cellular radiotelephone. It is. Second embodiment of the present invention
An object of the present invention is to quickly acquire position information in order to quickly execute a drop-off or hand-off operation.

[0025]

SUMMARY OF THE INVENTION The above objects and further objects and advantages of the present invention are directed to a unique wireless telephone which uses a cellular radiotelephone having a positioning system for acquiring satellite signals and establishing the exact location of the cellular radiotelephone. This is achieved by providing a method. This location information can be transferred to the cell base station for dropping off or handing off the cellular radiotelephone to another base station or frequency based on the quality level of the communication signal. Preferably, the system uses code division multiple access techniques. Preferably, the positioning system is a satellite positioning system (GPS) that receives signals from at least one communication satellite.

The method of the present invention can also be used to determine the closest base station to a cellular radiotelephone. The method also calculates a distance between the location where the quality level of the cellular radiotelephone communication signal is expected to be less than a predetermined value and the cellular radiotelephone, and based on the distance obtained by this calculation, It can also be used to determine whether to hand off a cellular radiotelephone. Preferably, the location of the cellular radiotelephone is determined using triangulation based on satellite signal timing. In one embodiment of the invention, each wireless telephone in a cell must register with a cell base station. The base station pages all wireless phones in the cell and requests their location. The calculation of the distance and the determination of whether to drop off or hand off the cellular radiotelephone are based on the location information of the cell base station and a predetermined distance value transmitted from the base station to the cellular radiotelephone. It is possible to carry out.

[0027]

DETAILED DESCRIPTION The following description is provided to enable any person skilled in the art to make and use the invention. The following description describes the best embodiment of the present invention considered by the inventor. However, various modifications will be immediately apparent to those skilled in the art. Because the principles of the present invention are specifically defined herein, a cellular communication device capable of acquiring satellite signals for position establishment is provided for smooth execution of drop-off and hand-off operations. .

In the satellite radio telephone of the present invention, CDMA
It is desirable to use a spread spectrum communication system such as This is because these systems provide the accuracy required for navigation coverage, direction finding, collision avoidance, automatic tracking, and investigation. Further, all conventional CDMA cellular communication systems have a base station connected to a satellite for clock synchronization. The base station
A positioning system terminal such as a satellite positioning system (GPS) terminal is used to determine the position of the satellite. Mitsubishi
Some cars, such as Montero, have GPS chips on them to determine the location of the car for navigation. In communication systems that already have GPS terminals, the base station message sent to each of the wireless telephones may include the satellite position. Furthermore, as described above, it is a known technique,
Each base station may transmit its own location information.
Usually, this position information includes latitude, longitude, and a predetermined distance limit.

FIG. 3 shows a typical wireless telephone 20 of the present invention. The radiotelephone 20 includes a positioning system 22 for determining a position on the earth. The positioning system 22 is preferably a satellite positioning system (GPS). This information is transferred to the base station 24 and may be used for drop-off and hand-off operations. Wireless telephone 20
Has a positioning system memory 26 that stores a database containing the ephemeris of each satellite. This memory 26 is desirably a non-volatile RAM, and causes the service radiotelephone 20 to update ephemeris data when the operation of the satellite is stopped or the satellite changes its orbit. In another embodiment, a programmable read-only memory in which the ephemeris of each satellite is permanently stored may be used. In still another embodiment,
A battery-backed RAM may be used.
The radiotelephone 20 also includes a real-time clock 28, a microprocessor 30 for controlling and calculating the operation of the radiotelephone 20, an antenna 32, a coder 34 for encoding and decoding a user's voice, and a modulation / demodulation circuit 38. ,
A code storage area 46 implemented by an EPROM or the like having an application software program 36, a keypad 44, and convert the modulated signal to a high frequency for transmission;
It includes conventionally used components, such as a radio frequency electronic circuit 42 that converts the received signal to a lower frequency.

Preferably, positioning system 22 transmits a spread spectrum signal. The spread spectrum signal is used to measure the range of wireless telephone 20 from a known satellite 40 location. The process of finding the signal of the satellite 40 is
The radio telephone 20 has its internal real time clock 2
It starts by synchronizing 8 with the satellite 40 system time. This system time is maintained by the internal clock of the satellite 40 and the base station 24. If this time and the ephemeris of each satellite 40 are known, the radio telephone 20 can simultaneously know the position of the satellite 40 corresponding to the earth. Thus, the available frequency and pseudo noise
(PN) code and satellite 40
To determine the frequency and the PN code to be searched in order to obtain the signal. To this end, the GPS receiver memory 26 database stores the signal carrier frequency of each satellite 40 so that the pilot satellite communication signal can be obtained and the position of the satellite 40 corresponding to the earth can be determined. Positioning system 2 in wireless telephone 20
2 terminal uses a known frequency and PN code to
The pilot carrier signal transmitted from 0 is determined.
Thereby, the wireless telephone 20 can identify the different satellites 40. Upon completion of the connection, the satellite 40 transmitter provides the location of the satellite 40 to the positioning system receiver 22 in the radiotelephone 20.

The radiotelephone 20 has to determine its position corresponding to the earth. This position is determined by triangulation using a plurality of different satellites 40, triangulation using a single satellite 40 taking different positions over time, or other conventional methods. Since the radiotelephone 20 knows the position of the satellite 40, it measures the time it takes for the signal to reach the satellite 40 and return to determine the position of the satellite corresponding to the receiver on earth. You may. Desirable is a method of calculating the above position by triangulation using receivers located at three different locations at the same time. This is because the difference in signal waveform between each receiver and transmitter is a function of time, and thus distance. Advanced GPS receivers have several receivers and can process signals from several satellites 40 at the same time. Low cost receivers use only one receiver. The receiver must continuously acquire and measure the range for at least three satellite signals.

The software program 36 can support certain communication protocols between the radiotelephone 20 and the base station 24 and includes the positioning system 22 and the radiotelephone, such as the microprocessor 30, the memory 26, and the keypad 44. To help connect with existing components. The software program 36 uses the microprocessor 3 to calculate the distance to the base station 24 and other distances.
0 may be included.

As a feature of the present invention, when base station 24 pages wireless telephones 20, base station 24 sends a message to each wireless telephone 20. This message may include information indicating the position of the satellite and the position of the base station 24. The location information of the base station 24 is usually latitude,
In addition to the longitude and the predetermined distance limit, the parameter includes parameters used by the microprocessor 30 in the wireless telephone 20 to detect whether the candidate is a handoff or a dropoff. The radiotelephone 20 may detect whether it is a candidate for handoff or dropoff, and this information may be forwarded in a message to the base station 24.

In another embodiment, the base station 24 periodically broadcasts the latitude and longitude parameters from each wireless telephone 20 in the cell when determining whether to perform a handoff or a dropoff. , And retain this information for future use, the base station 24
Since it has information about its own latitude and longitude, it calculates the distance between itself or the low signal area and each radiotelephone 20 by means of periodic or emergency broadcasts, the same or different It may indicate either a handoff of the frequency to another base station, a handoff to a different frequency within the same base station, or a dropoff.

In yet another embodiment, the base station 2 is only activated if the base station 24 estimates that one of the radiotelephones in the cell should be handed off or disconnected.
4 requests the location data of the radiotelephone 20, and upon receiving this request, the radiotelephone 20 obtains its own position from the position of the satellite 40 and sends this information to the base station 24.

Either way, if the active radiotelephone 20 is expected to enter the area where poor reception occurs, it will be dropped off or handed off before the radiotelephone 20 degrades the operation of the other radiotelephones. like,
A special warning signal may be sent from the base station 24 to the wireless telephone 20. As previously described in connection with the radiotelephone 20 moving between cells, the method of obtaining accurate location information of the radiotelephone 20 using GPS and sending that information to the base station is based on It should be understood that at the time of initial power-on, it is very useful in determining the safety of operation. Further, the same method and apparatus may be used to quickly determine the base station closest to wireless telephone 20, ie, the base station controlling wireless telephone 20.

In addition, some communication technologies require the location of the wireless telephone to be known. For example, power control CDMA
In the system, each wireless telephone adjusts the increase or decrease in transmission power based on the distance from the base station. Thereby, the input signals received by the base station all have the same power. According to a preferred embodiment of the present invention, the radiotelephone obtains the distance from the base station with high accuracy in order to calculate based on the exact position of the radiotelephone 20 determined by GPS, A more accurate transmission signal power level is obtained.

The wireless telephone 20 of the present invention preferably employs a positioning system 22 implemented as a GPS chip. Positioning system 22 may be incorporated into wireless telephone 20. It is desirable that this chip can be turned on and off freely in order to save power when handoff using GPS is not desired. Alternatively, the GPS terminal may be an accessory attached to the outside of the wireless telephone 20 that can be attached to an internal component of the wireless telephone 20 by a connector (not shown). This accessory may use a radiotelephone keypad 44 for user commands. In any case, communication with the base station 24 is realized by the application software 36 stored in the code storage area 46 in the wireless telephone.

Although the radiotelephone system in the preferred embodiment of the present invention is adaptable to any cellular communication system, in particular, to prevent handoffs from being exceeded when selecting the best base station, Applicable to GSM cellular radiotelephone using Code Division Multiple Access (CDMA) technology. Other embodiments include time division multiple access (TDMA) and frequency division multiple access (FDMA).
Embodiments using other cellular communication systems such as DMA) are possible. The method of the present invention can also be used for AMPS to prevent excessive frequency hopping. Current,
Inexpensive cellular radiotelephones use analog radiotelephones that can only tune to one frequency at a time. When the signal weakens, the audio signal is cut off by the base station. This is because there is a high risk of destruction if the wireless telephone waits for milliseconds while trying to tune itself to a different frequency. In the cellular radiotelephone of the present invention, the base station can determine the base station having the best signal upon handoff.
This allows the wireless telephone to perform a smooth handoff and connect to the current base station longer. This reduces the number of dropped calls.

The present invention also overcomes the disadvantages noted in the IS-95A standard. This is because the cellular radiotelephone does not have to be set to analog mode forever after switching to analog mode in the reception area under the disadvantageous conditions of weak digital transmission. A radiotelephone using a GPS system can receive a warning signal from a base station before entering a weak signal area such as a tunnel and switch itself to another frequency or AMPS system if analog is possible. is there. This makes it possible to prevent the entire system from deteriorating. After the signal is as strong as before, the wireless telephone can switch back to itself. The base station periodically receives accurate location information from each cellular radiotelephone and has information for warnings due to the fact that it can predict the future location of that radiotelephone by calculating speed and direction of travel. Things. Since the base station can store the map of the cell in the computer, it can know the area where the weak signal occurs and detect a wireless telephone approaching such an area.

Those skilled in the art will recognize that various adaptations and modifications to the preferred embodiment described above are conceivable without departing from the scope and spirit of the invention. Thus, in the claims appended hereto, the invention may be practiced other than as specifically described herein, and may include transmitting information from a cellular device to a base station, It will be appreciated that implementations are possible on similar devices such as modems, fax machines, and the like.

[Brief description of the drawings]

The objects and features of the invention believed to be novel are set forth with particularity in the appended claims. The structure and manner of operation of the present invention, together with further objects and features of the invention, will be best understood by referring to the following description, taken in conjunction with the accompanying drawings, in which the components are indicated by reference numerals. .

FIG. 1 shows a wireless telephone in a typical cellular communication system cell network.

FIG. 2 shows an example of a cellular communication system network.

FIG. 3 illustrates components of a wireless telephone according to a preferred embodiment of the present invention.

Claims (30)

[Claims] An apparatus for transmitting and receiving communication signals between a plurality of cellular radiotelephones and each of the cellular radiotelephones.
A communication system comprising at least one base station, wherein at least one of the cellular radiotelephones includes a positioning system for transmitting a signal to the earth.
Determining the exact position of the cellular radiotelephone by communicating with two communication satellites using satellite signal data, the base station determines that the quality level of the communication signal of the cellular radiotelephone including the positioning system is higher than a predetermined value. Is expected to decrease before system degradation occurs.
A communication system for determining drop-off or hand-off based on a location of a cellular radiotelephone including said positioning system. 2. The communication system according to claim 1, wherein the communication signal is a CDMA signal. 3. The communication system according to claim 1, wherein the position of the cellular radiotelephone including the positioning system is determined using triangulation based on the timing of the satellite signal. 4. The communication system according to claim 1, wherein the handoff of the cellular radiotelephone including the positioning system includes a handoff to another different base station. 5. The communication system according to claim 1, wherein the handoff of the cellular radiotelephone including the positioning system includes a handoff to another different frequency. 6. The positioning system is a GPS, the cellular radiotelephone further includes a storage area for storing ephemeris data of the communication satellite, a clock for synchronizing with the communication satellite, and a software program. 2. The communication system according to claim 1, further comprising: a code storage area that stores a program; and a microprocessor that executes the software program. 7. The communication system according to claim 6, wherein the GPS is an optional accessory, is not included in the cellular radio telephone, and can be freely attached to the cellular radio telephone. 8. The communication system according to claim 6, wherein said software program determines a base station closest to said cellular radiotelephone. 9. The software program of claim 6, wherein the software program registers the cellular radiotelephone with the base station, replies to a page from the base station, and transmits the location of the cellular radiotelephone to the base station. Communication system. 10. The software program calculates a distance between the cellular radiotelephone and a location where a quality level of a communication signal of the cellular radiotelephone is expected to be smaller than a predetermined value. 10. The communication system according to claim 9, wherein it is determined from the distance whether the cellular radiotelephone should be handed off. 11. The software program calculates a distance between the cellular radiotelephone and the base station and determines from the calculated distance whether the cellular radiotelephone should be handed off. 10. The communication system according to 9. 12. The software program calculates a distance between the cellular radiotelephone and the base station, and calculates a distance between the location of the base station and a predetermined distance value transmitted to the cellular radiotelephone by the base station. 10. The communication system according to claim 9, wherein the communication system determines whether or not the cellular radiotelephone should be dropped off according to: 13. The base station calculates a distance between the cellular radiotelephone including the positioning system and the base station, and determines from the calculated distance whether the cellular radiotelephone should be handed off. 2. The communication system according to claim 1, wherein 14. The base station calculates a distance between a cellular radiotelephone including the positioning system and a position where a quality level of a communication signal of the cellular radiotelephone is expected to be smaller than a predetermined value. The communication system according to claim 1, wherein it is determined whether the cellular radiotelephone should be handed off from the calculated distance. 15. The communication system of claim 1, wherein the base station sends a page only when a particular one of the cellular radiotelephones containing the positioning system may need to be handed off. 16. The base station calculates a distance between a cellular radiotelephone including the positioning system and the base station and determines from the calculated distance whether a cellular telephone should be dropped off. 2. The communication system according to claim 1, wherein 17. A communication method for use in a cellular radiotelephone controlled by at least one base station that transmits and receives communication signals, the method comprising: determining an accurate position in response to a signal received from at least one communication satellite; A first determining step of determining the exact position of the cellular radiotelephone using a positioning system for determining the quality level of the communication signal of the cellular radiotelephone in advance according to the position of the cellular radiotelephone A second determining step of determining, the quality level of the communication signal of the cellular radiotelephone is the first
A first execution step of performing a drop-off of the cellular radiotelephone when it is expected to be smaller than a predetermined value of
Performing a handoff of the cellular radiotelephone when it is expected that the cellular radiotelephone will be smaller than a predetermined value. 18. The communication method according to claim 17, wherein the handoff of the cellular radiotelephone including the positioning system includes a handoff to another different base station. 19. The communication method according to claim 17, wherein the handoff of the cellular radiotelephone including the positioning system includes a handoff to another different frequency. 20. The communication method according to claim 17, wherein the communication signal is a CDMA signal, and the positioning system includes a GPS. 21. The first determining step is performed using trigonometry according to the timing of a satellite signal.
The communication method according to item 17. 22. Each of the base stations controls a plurality of cellular radio telephones, a registration step of registering each of the cellular radio telephones with a base station, a reply step of returning a page from the base station, 18. The communication method according to claim 17, further comprising: transmitting a position of the cellular radio telephone to the base station. 23. A calculating step for calculating a distance between the cellular radiotelephone and a position where a quality level of a communication signal of the cellular radiotelephone is expected to be smaller than a second predetermined value; Deciding whether the cellular radiotelephone should be handed off from the calculated distance. 24. Calculating the distance and deciding whether to handoff the cellular radiotelephone,
24. The communication method according to claim 23, which is performed in the base station. 25. Calculating the distance and deciding whether to hand off the cellular radiotelephone,
24. The communication method according to claim 23, wherein the communication method is executed in the cellular wireless telephone. 26. The communication method of claim 22, wherein returning the page is performed only when a particular one of the cellular radiotelephones is to be handed off. 27. The communication method according to claim 17, wherein the base station performs drop-off of the cellular radio telephone based on a position of the cellular radio telephone. 28. calculating a distance between a location where the quality level of the cellular radiotelephone communication signal is expected to be less than the first predetermined value and the cellular radiotelephone; Determining whether to drop off the cellular radiotelephone based on the distance traveled. 29. Calculating a distance between a position where the quality level of the cellular radiotelephone communication signal is expected to be smaller than the first predetermined value and the cellular radiotelephone, and a distance obtained by the calculation. 29. The communication method according to claim 28, wherein the step of determining whether to drop off the cellular radiotelephone based on is performed in the cellular radiotelephone. 30. The method of claim 17, further comprising calculating a distance between said cellular radiotelephone and said base station.
Communication method described in.